Clutch assembly with formed retention ring

ABSTRACT

A clutch assembly for a vehicle transmission includes a housing defined by a wall having an annular configuration circumscribing a clutch axis. The wall extends between an open end and a floor. The floor extends inwardly from the wall toward the clutch axis. A plurality of splines formed in the wall and each is spaced from the open end of the housing. A snap ring retains clutch plates in the housing. The open end of the wall is deformed inwardly toward the clutch axis defining a retainer for retaining the snap ring within the housing.

BACKGROUND OF THE INVENTION

The present invention relates generally toward a clutch for use in anautomotive transmission. More specifically, the present inventionrelates toward an improved clutch housing and retention assembly.

Clutches are known to be used in an automatic transmission assembled toa power train of a vehicle. An increased number of clutches assembledinto a transmission are also known to improve mileage performance of avehicle. For example, a transmission having only four clutches does notperform as well, or provide as good mileage performance, as atransmission having six, or even eight clutches. Due to the increasingcost of fuel, most vehicle companies are engineering new transmissionshaving eight and even nine clutches.

A typical clutch includes an annular housing having an annular walldefining a plurality of spaced splines. These splines are typicallyformed by a process known as “lance-and-form” to provide a gear-likeinterface with a plurality of clutch plates retained inside the clutchhousing. Occasionally, the splines are formed in the annular wall bymachining a substantially thicker housing when additional structuralintegrity is required. Inside the clutch housing, a piston is retainedadjacent a base of the housing and circumscribes a transmission shaftthrough which oil flows in between the housing base and the piston. Thepiston is separated from the plurality of clutch plates by a steelspacer.

The splines that are defined by the annular wall of the housing extendto the distal end of the housing. A snap ring groove is formed into thesplines by either a machining or a reverse lance-and-form process. Asnap ring is inserted into the groove to retain the clutch componentsset forth above. Clutches typically fail because the weakness of thereverse lance-and-formed groove formed into the splines of the clutchhousing. Sharp edges defined by the reverse lance create weaknesses inthe housing that are known to crack, particularly when the transmissionsare under heavy load. Attempts have been made to improve the integrityof the snap ring groove and the clutch housing by increasing thethickness of the clutch housing and extending the distance between thesnap ring groove and the open end of the housing. None of these attemptsto improve the integrity of the housing have proven sufficient.Furthermore, increasing the thickness of the housing adds weight to thevehicle transmission, particularly given eight clutches are becomingmore prevalent in some transmissions. Furthermore, extending thedistance between the snap ring groove and the end of the clutch housingmakes use of packaging space unnecessarily causing increase inside atransmission. Therefore, there is a strong need to redesign the clutchand the clutch housing to reduce mass, increase structural integrity,particularly to retain the snap ring, and reduce the amount of packagingspace required for a given clutch.

SUMMARY OF THE INVENTION

A clutch assembly for a transmission, particularly for a vehicletransmission, includes a housing defined by a wall having an annularconfiguration circumscribing a clutch axis. The wall extends between anopen end and a floor and the floor extends inwardly from the wall towardthe clutch axis. A plurality of splines is formed in the wall and thesplines are spaced from the open end of the housing. The snap ringretains a plurality of clutch plates and fibrous plates in the clutchhousing. The open end of the wall is deformed inwardly toward the clutchaxis at the open end of the housing defining a retainer for retainingthe snap ring within the housing.

The inventive clutch and clutch housing eliminates the lance-and-formsnap ring groove known to prior art clutch housings, which typicallycauses failure in an automotive transmission. The retainer of thepresent clutch housing is defined by deforming an annular wall of thehousing radially inwardly to define the retainer between the upper endof the splines and the deform wall. In effect, the snap ring retentionis achieved by “hemming” the top of the housing and results in a full360° retention. This configuration of the snap ring retainer eliminatesthe weaknesses associated with the prior art lance-and-formed snap ringgroove that are caused from forming a reverse lance cut in the pluralityof splines formed in the clutch housing. This lance cut causes a stressrising condition resulting a release of the snap ring from the clutchhousing. It is believed that the thickness of the clutch housing can nowbe reduced by upwards of 0.5 millimeters providing a 20% decrease in themass of a typical housing. Furthermore, the splines no longer extend tothe open end of the clutch housing, but are spaced from the open end ofthe housing to facilitate the deformation of the open end to form theretainer from the snap ring. This facilitates a reduction of the axiallength of the clutch housing reducing the packaging space required ofeach clutch of the automotive transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, willbecome readily apparent to those skilled in the art from the followingdetailed description of a preferred embodiment when considered in lightof accompanying drawings in which:

FIG. 1 shows a cross-sectional view of the clutch of the presentinvention;

FIG. 2 shows a fragmented, perspective view of the clutch housing ofFIG. 1;

FIG. 3 shows a plan view of the clutch housing of the present invention;

FIG. 4 is a sectional view of line 4-4 of FIG. 3 showing an installationof an individual clutch plate;

FIG. 5 is a sectional view of line 5-5 of FIG. 3 showing an installationof an individual clutch plate;

FIG. 6 shows a partial plan view of a clutch plate;

FIG. 7 shows a partial plan view of the inventive clutch assembly havinga clutch plate installed;

FIG. 8 shows a partial plan view of a clutch assembly having a clutchplate and a retention or snap ring installed;

FIGS. 9 and 10 shows a sectional view of the retainer and retainer teethwith the snap ring installed;

FIG. 11 shows a partial perspective view of the clutch housing prior toforming the retainer;

FIG. 12 shows a partial sectional view of the clutch housing prior toforming the retainer;

FIG. 13 shows a partial perspective view of the clutch housing havingretention teeth formed prior to forming the retainer;

FIG. 14 shows a partial perspective view of an alternative clutchhousing of the present invention; and

FIG. 15 shows a partial sectional view having a retainer ring and clutchplates installed into the alternative clutch housing.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a side sectional view of the clutch assembly of thepresent invention is generally shown at 10. The assembly 10 includes ahousing 12 defined by an annular wall 14. The annular wall 14circumscribes a transmission shaft 16 that defines a shaft axis A. Theannular wall 14 of the housing 12 extends axially between an open end 18and a floor 20. The floor 20 extends radially inwardly toward thetransmission shaft 16. A piston 22 circumscribes the transmission shaft16 and is positioned adjacent the floor 20 of the housing 12. A seal 23seals the floor 20 of the housing 12 to the transmission shaft 16.Transmission fluid pumps through the transmission shaft 16 throughoutlets 24 and to the space located between the piston 22 and the floor20 of the housing 12 to shift the clutch assembly 10 in a known manner.A fibrous plate 28 circumscribes the transmission shaft 16 and ispositioned in an abutting relationship between the piston 22 and aplurality of clutch plates 26. The clutch plates 26 are separated byfibrous plates 28. Clutch plates 26 and the fibrous plates 28circumscribe the transmission shaft 16 and are retained in the housing12 by snap ring 30 as will be explained further herein below. A clutchpressure plate 32 is disposed between the plurality of clutch plates 26,the fibrous plates 28, and the snap ring 30. A shift member 34 overliesthe open end 18 of the housing 12 and provides biasing support tobiasing member 36 for biasing the piston 22 toward the floor 20 of thehousing 12.

The housing 12 defines a plurality of housing splines 38 spaced around afull 360° of the housing 12 as best shown in FIG. 2. The shift member 34defines a plurality of member splines 40 as seen in FIG. 1 so that thehousing splines 38 and the member splines 40 are opposed enablingpositioning of the clutch plates 26 engage either the housing splines 38or the member splines 40 as shown in FIG. 1. Therefore, it should beunderstood by those of ordinary skill in the art that the clutch plates26 define a plurality of spaced teeth 42 that engage the housing splines38 in a gear-like manner. The teeth 42 of the clutch plates 26 are bestrepresented in FIG. 6.

Referring now to FIG. 2, a retainer 44 is positioned at the open end 18of the housing 12. The retainer 44 extends radially inwardly toward thetransmission axis A and defines a plurality of retainer teeth 46. Eachof the retainer teeth 46 is circumferentially aligned with one of theplurality of housing splines 38, the purpose of which will be explainedfurther below. Each of the housing splines 38 are spaced from the openend 18 of the housing 12 so that a space 48 is defined between theretainer 44 and the housing splines 38. As shown in FIG. 1, a snap ring30 is located in space 48 defined between the retainer 44 and thehousing splines 38. Referring again to FIG. 2, the housing splines 38are also spaced from the floor 20 of the housing 12. Although thehousing splines 38 are represented as an inwardly projecting deformationin the annular wall 14 of the housing 12, it should be understood tothose of ordinary skill in the art that the housing splines 38 may beformed by a cold formed process.

Referring now to FIGS. 3-5, the plurality of housing splines 38 define aminor housing diameter 50 of the housing 12 and the annular wall 14 ofthe housing 12 defines a major housing diameter 52. Likewise, theretainer 44 defines a major retainer diameter 54 between each of theretainer teeth 46 and a minor retainer diameter 56 defined by theradially inwardly-most portion of the retainer teeth 46. It iscontemplated by the inventor that the major retainer diameter 54includes a length that is between the minor housing diameter 50 and themajor housing diameter 52. However, it is necessary that the majorretainer diameter 54 is greater than the outer-most diameter of theteeth 42 on the clutch plates 26. Further, the minor retainer diameter56 is contemplated to be proximate the minor housing diameter 50.However, the minor retainer diameter 56 should be no less than a minordiameter of the clutch plates 26.

The diameters as set forth above of the various elements of the housing12, the retainer 44, and the retainer teeth 46 facilitate theinstallation of the clutch plates 26 into the housing 12.

FIG. 7 shows a partially assembled clutch assembly 10 where a clutchplate 26 is shown being received by the housing splines 38 and theretainer teeth 46. The clutch plate teeth 42 are shown spaced from themajor housing diameter 52. It should be understood by those of ordinaryskill in the art that the clutch plate teeth 42 need merely bereceivable by the retainer 44 and be engagable with the housing splines38 to be fully operable.

FIG. 8 shows another view of a partially assembled clutch assembly 10having the snap ring 30 retained by the retainer 44 and being positionedin the space 48 between the housing splines 38 and the retainer 44.

Referring to FIGS. 9 and 10, the snap ring 30 is shown positioned in thespace 48 defined between the retainer 44 and the housing splines 38. Itshould be apparent by FIG. 10 that the snap ring 30 achieves 360° ofcontact and retention by the retainer 44. As set forth above, prior artsnap ring grooves have only provided 180° of partial contact to the snapring resulting in localized stresses developing on the prior art housingcausing known failures. Additional structural integrity is shown in FIG.9 where the retainer teeth 46 provide 180 degrees of further contact andretention to the snap ring 30. It is believed that a 20% reduction inthe thickness of the sheet metal used to form the housing 12 isachievable by virtue of the increased contact between the retainer 44and the snap ring 30 versus the current lance-and-form snap ring groovedesign.

The method of forming the retainer will now be explained. Referring toFIG. 11, a partial cross-sectional view of the housing 12 is shown priorto formation of the retainer 44. Therefore, one of the plurality ofhousing splines 38 is shown having a diameter less than an upper flange58 of the partially formed housing 12. It is obvious to one of ordinaryskill in the art that the housing splines 38 are clearly spaced from anopen end of the housing 12, even prior to full formation of the retainer44. A fragmented line 6 shows the target hem of the flange 58 to definethe retainer 44, and therefore the space 48, disposed between theretainer 44 and the plurality of housing splines 38. It should be notedthat hem material thickness is constant of the parent incoming materialthickness used on the entire clutch housing. However, prior to formingthe housing flange 58, the housing flange 58 is slotted to define theretainer teeth 46, as best represented in FIG. 13. Once the retainerteeth 46 have been slotted into the flange, the retainer 44 is formed bya rolling or flow forming a process to define the space 48 disposedbetween the retainer 44 and the housing splines 38 as seen in FIGS. 9and 10. It should be further understood by those of skill in the art,that the space 48 defined between the retainer 44 and the housingsplines 38 is constant, while the snap ring 30 is selected from aplurality of thicknesses to accommodate assembling a variation of theclutch assembly 10. Therefore, it is believed the snap ring 30 will havesome float within the space 48 defined by the retainer 44 and thehousing splines 38 dependent upon the thickness of the snap ring 30selected at the time of assembly.

An alternative retainer 60 is represented in FIGS. 14 and 15. Elementsthat are the same as those disclosed in the prior embodiment include thesame element numbers. The alternative retainer 60 defines an outerretainer wall 62 having a diameter greater than the major housingdiameter 52. In this embodiment, the alternative retainer 60 does notinclude retainer teeth, but provides a more extensive overlap with thesnap ring 30, as is best represented in FIG. 15. In this embodiment,additional contact with the snap ring 30 is made by the retainer so that360° of contact is achieved with a more substantial portion of thealternative retainer 60 by way of alternative retainer lip 64. Asfurther represented in FIG. 15, snap ring 30 includes an outer diameterthat is greater than the major housing diameter 52. However, snap ring30 provides sufficient overlap with the pressure plate 32, the clutchplates 26, and the fibrous plates 28 to adequately retain the clutchassembly 10.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationwhile material to the teachings of the invention without departing fromthe essential scope thereof. Therefore, it is intended that theinvention not be limited to the particular embodiment disclosed as thebest mode contemplated for carrying out this invention but that theinvention will include all embodiments falling within the scope of theappended claims.

What is claimed is:
 1. A clutch assembly for a transmission, comprising:a housing defined by a wall having an annular configurationcircumscribing a clutch axis, said wall extending between an open endand a floor, said floor extending inwardly from said wall toward saidclutch axis; a plurality of splines formed in said wall, said splinesbeing spaced from said open end of said housing; a snap ring forretaining clutch plates in said housing; and said open end of said wallbeing deformed inwardly toward said clutch axis defining a retainer forretaining said snap ring within said housing.
 2. The assembly set forthin claim 1, wherein said wall of said housing includes a major housingdiameter and a minor housing diameter, said retainer defining a minorretainer diameter being truncated between said major housing diameterand said minor housing diameter.
 3. The assembly set forth in claim 1,wherein said retainer provides three hundred sixty degrees of contactretention to said snap ring.
 4. The assembly set forth in claim 1,comprising a plurality of tabs extending radially inwardly from saidretainer.
 5. The assembly set forth in claim 4, wherein said tabscircumferentially overly said splines.
 6. The assembly set forth inclaim 1, wherein said snap ring comprises a plurality of snap rings eachhaving a different thickness for accommodating variation of said clutchplates.
 7. The assembly set forth in claim 1, wherein said clutch platesinclude a peripheral edge and said peripheral edge defines a pluralityof plate teeth of thereby defining a plate major diameter, said platemajor diameter being lesser than said housing major diameter.
 8. Theassembly set forth in claim 1, wherein said splines formed in said wallof said housing are spaced from said floor of said housing.
 9. Theassembly set forth in claim 1, wherein said retainer includes a retainerwall having a diameter greater than said major housing diameter.
 10. Theassembly set forth in claim 1, including a plurality of clutch ringsbeing retained within said clutch housing by said snap ring.
 11. Aclutch housing for use in a transmission, the housing enclosing clutchplates interacting with a drive shaft of a vehicle, comprising: a wallhaving a tubular configuration with an open end and a partially closedend, said partially closed end having a floor extending radiallyinwardly from said wall; a plurality of splines formed into said wallthereby providing gear like engagement with the clutch plates disposedinside said housing, said plurality of splines being spaced from saidopen end of said wall; and a retainer defined by a hem at said open endof said wall, said hem extending radially inwardly from said wall forretaining a snap ring used to retain the clutch plate assemblies withinsaid clutch housing.
 12. The clutch housing set forth in claim 11,comprising a plurality of tabs extending radially inwardly from saidretainer.
 13. The clutch housing set forth in claim 12, wherein each ofsaid tabs are circumferentially aligned with one of said plurality ofsplines formed in said wall of said clutch housing.
 14. The clutchhousing set forth in claim 11, wherein said plurality of splines arespaced from said floor of said clutch housing.
 15. The clutch housingset forth in claim 11, wherein each of said plurality of splines definea continuous surface.
 16. The clutch housing set forth in claim 11,wherein said retainer defines a space with said plurality of splines forreceiving a snap ring.
 17. The clutch housing set forth in claim 11,wherein said retainer defines an outer retainer wall having a diametergreater than a major diameter of said wall of said housing.
 18. Theclutch housing set forth in claim 11, wherein said retainer defines amajor retainer diameter, said splines define a minor spline diameter andsaid housing defines a major housing diameter, said retainer majordiameter being greater than said minor spline diameter and said majorhousing diameter.
 19. The clutch housing set forth in claim 11, whereinsaid clutch plates include a plurality of teeth for engaging saidplurality of splines and said clutch teeth define a major teeth diameterbeing less than said major retainer diameter.
 20. The clutch housing setforth in claim 11, wherein said retainer engages said snap ring alongthree hundred sixty degrees of said wall having a tubular configuration.